{!../../../docs_src/wsgi/tutorial001.py!}
```

## Check it

Now, every request under the path `/v1/` will be handled by the Flask application.

And the rest will be handled by **FastAPI**.

If you run it and go to <a href="http://localhost:8000/v1/" class="external-link" target="_blank">http://localhost:8000/v1/</a> you will see the response from Flask:

```txt
Hello, World from Flask!
```

    * This will be done by sending a POST request (from *your API*) to some *external API* provided by that external developer (this is the "callback").

## The normal **FastAPI** app

Let's first see how the normal API app would look like before adding the callback.

It will have a *path operation* that will receive an `Invoice` body, and a query parameter `callback_url` that will contain the URL for the callback.

// If the call is canceled through the context,
// the appropriate error will be returned.
type Stream struct {
	// responses from the remote server.
	// Channel will be closed after error or when remote closes.
	// All responses *must* be read by the caller until either an error is returned or the channel is closed.
	// Canceling the context will cause the context cancellation error to be returned.
	responses <-chan Response

}

// CronJobSpec describes how the job execution will look like and when it will actually run.
message CronJobSpec {
  // The schedule in Cron format, see https://en.wikipedia.org/wiki/Cron.
  optional string schedule = 1;

  // The time zone name for the given schedule, see https://en.wikipedia.org/wiki/List_of_tz_database_time_zones.
  // If not specified, this will default to the time zone of the kube-controller-manager process.

!!! info
    These docs are about to be updated. 🎉

    The current version assumes Pydantic v1.

    The new docs will hopefully use Pydantic v2 and will use <a href="https://art049.github.io/odmantic/" class="external-link" target="_blank">ODMantic</a> with MongoDB.

!!! warning "Deprecated"
    This tutorial is deprecated and will be removed in a future version.

* Those schemas will be part of the generated OpenAPI schema, and used by the automatic documentation <abbr title="User Interfaces">UIs</abbr>.

## Automatic docs

The JSON Schemas of your models will be part of your OpenAPI generated schema, and will be shown in the interactive API docs:

<img src="/img/tutorial/body/image01.png">

### Technical Details: `root_path`

When you mount a sub-application as described above, FastAPI will take care of communicating the mount path for the sub-application using a mechanism from the ASGI specification called a `root_path`.

That way, the sub-application will know to use that path prefix for the docs UI.

}

// csvSplitSize is the size of each block.
// Blocks will read this much and find the first following newline.
// 128KB appears to be a very reasonable default.
const csvSplitSize = 128 << 10

// startReaders will read the header if needed and spin up a parser
// and a number of workers based on GOMAXPROCS.
// If an error is returned no goroutines have been started and r.err will have been set.

requests to the agent, causing the agent to submit a CSR to the configured CA (generally Istiod). For other configuration,
Envoy will send [ADS](https://www.envoyproxy.io/docs/envoy/latest/intro/arch_overview/operations/dynamic_configuration#aggregated-xds-ads)

configuration using e.g. the `mc admin config` commands you will need to adjust
your deployment.

Even though this change is backward compatible we do not expect that it affects
the vast majority of deployments in any negative way.

> Will an upgrade of an existing MinIO cluster impact the SLA of the cluster or will it even cause downtime?